I have both FPV and the Codec pack. I noticed that there was an update of FPV available and updated to it. It seemed to also update my codec pack as well. I know that the codec pack has extra features. Is there need to update the codec pack separately?

Yes FPV Pro and the FPV Codec Pack are two distinct products (with a bit of overlap). If you want to benefit from the new feature of the Codec Pack (like the 3 new codecs introduced in v3.1, or updates to the codecs contained in the Codec Pack and which are not part of FPV Pro) then you should update both packages. The viewer comes with the same raw codecs as those in the Codec Pack, but the latter adds about 13 on its own.

What codec is required to import AVI files into Windows Movie Maker and where can I download said codec? Every time I try to import my AVI files to make a music video it says that the required codec is not installed on my computer. I set my computer to download them automatically and the error message still pops up. Can anyone help me?